re-sizing pictures on a Mac for our wedding website..?

Agh, I have tried what feels like a gazillion ways to re-size our pictures for our wedding website. (knot.com). We got back all of our engagement pictures and I am so pumped/excited to upload them…. But, I can’t since they’re just over the MB they allow (8) apparently.

Does anyone have a mac and can help me with this..? LOL. I’m in momzbie mode and google didn’t seem to be to much help. LOL.